1. Field of the Invention
The present invention relates to a data control apparatus, and more particularly to a data control apparatus for managing data possessing of time information.
2. Description of the Prior Art
In this specification, the time information denotes the information expressing part or the whole of the year, month, day and time, and the period means both a closed period determined by the start point and the end point, and an open period determined either by the start point or the end point.
The data control apparatus for managing the data possessing of time information such as year, month and day is known. In the conventional data control apparatus for managing the data possessing of year, month and day as the time information, when the date to determine the start point of the research period and the date to determine the end point of the research period are given by the operator as the data research conditions, the data having the accompanying date contained in the research period set by the operator is selected from among the data stored in the memory device of the apparatus.
In such data search using the data control apparatus, it is often required to search in the unit of year or the unit of month. For example, when searching the data in 1989, the start point of the research period to be set in January 1, 1989, and the end point of research period is December 31, 1989. In another example, when searching the data in April 1989, the start point of research period to be set is April 1, 1989, and the end point of research period is April 30, 1989.
As understood from these examples, in the data searching in the unit of year, the start point and end point of research period to be set are always the same. In the data searching in the unit of month, the start point and end point depend on each month.
In the conventional data control apparatus, when searching the data, it is always necessary to set both the start point and end point of the research period. Therefore, in the conventional data control apparatus, the input job for data retrieval is bothersome for the operator who searches in the year unit or month unit, and the retrieval work is time-consuming.